Not Applicable
Not Applicable
1. Field of the Invention
The present invention relates to a bipolar plate for a fuel cell, in particular, a corrugated bipolar plate made of metal. The bipolar plate provided by this invention can simplify the manufacturing process of the fuel cell and thus, reduce the production costs. Specially, the dimension and weight of the fuel cell can be decreased such that the actual utilization and mass production of the fuel cell become more convenient and practical.
2. Description of the Related Art
With the rapid growth of human civilization, the consumption of traditional energy sources, such as coal, oil and natural gas, increases rapidly. This has resulted in a serious pollution to the global environment, as well as various environmental problems such as global warming and acid rain. It is now recognized that the natural energy resources are limited. Therefore, if the present rate of consumption continues, all existing natural energy sources will be exhausted in the near future. Accordingly, many developed countries are dedicated to research and development of new and replaceable energy sources. The fuel cell is one of the most important and reasonably priced choices. Compared with traditional internal combustion engines, the fuel cell has many advantages such as high energy transformation efficiency, clean exhaust, low noise, and no consumption of traditional gasoline.
In brief, a fuel cell is an electrical power generation device powered by the electrochemical reaction of hydrogen and oxygen. In basic terms, the reaction is a reverse reaction of the electrolysis of water, to transfer the chemical energy into electrical energy. The basic construction of a fuel cell, for example, a proton exchange membrane fuel cell, comprises a plurality of cell units. The construction of the cell unit can be generally illustrated in FIG. 1. It comprises a proton exchange membrane (PEM) 10 at the middle, with the two sides thereof provided with a layer of catalyst 12, each of the two outsides of the catalyst 12 being further provided with a gas diffusion layer (GDL) 14. An anode plate 16 and a cathode plate 18 are further provided at the outermost sides adjacent to the GDL 14. After tightly combining all the above elements together, a cell unit is formed. For the practical application of a fuel cell, a plurality of the above cell units are stacked and serially connected to provide sufficient power, as illustrated in FIG. 2. Therefore, two adjacent cell units can share a common polar plate 20, as illustrated in FIG. 3, which serves as the anode and the cathode for the two adjacent cell units respectively. Accordingly, such a polar plate 20 is usually referred to as a bipolar plate.
Generally, as illustrated in FIG. 3, the two sides of the bipolar plate 20 are provided with many grooves 22 for transporting the gases for reaction, such as hydrogen and air (to provide oxygen), as well as moving the reactants, such as water droplet or vapor, out of the bipolar plate 20. The conventional bipolar plate 20 is made of pure graphite or a graphite composite. Thus, the grooves on the graphite plate are usually formed by additional mechanical machining with complicated processes and at considerable cost. In addition, if the graphite plate is made by the compression molding of graphite powder, it must be further coated with resin or other material to seal the voids thereof. Moreover, graphite plate has a relatively low extensibility and thus cracks can be formed very easily. The crack on the bipolar plate may introduce leakage of gas and thereby impair the operation efficiency of the fuel cell. Furthermore, due to the requirement of adequate mechanical strength, the thickness of the graphite plate cannot be very thin, so the overall dimension occupied by the fuel cell cannot be further reduced.
It is a primary objective of this invention to overcome the disadvantages of the conventional bipolar plate and to provide a bipolar plate that is thin, light, made by a simplified process, and has a low cost to manufacture. Accordingly, the space occupied by the fuel cell can be reduced and the manufacturing cost of the fuel cell can be lowered, so that the fuel cell is suitable for mass production and commercialization.
The major technical content of this invention is to make a corrugated bipolar plate from a metal sheet and form a plurality of parallel grooves which are complementary to each other on the two side surfaces of the bipolar plate. Because the bipolar plate of this invention is made of metal, the thickness thereof can be relatively thin and, the dimension and weight of the fuel cell can be significantly reduced. In addition, the manufacturing processes of the bipolar plate are simplified and the relative costs can be decreased.
The structures and characteristics of this invention can be realized by referring to the appended drawings and explanations of the preferred embodiments.